High voltage connection to ignition coils

ABSTRACT

The ignition coil includes a cast resin portion; a primary winding embedded in the cast resin portion; a secondary winding embedded in the cast resin portion; at least one contact part electrically connecting an end portion of an ignition cable and a high-voltage end of the secondary winding; a retaining part (4) having a throughgoing aperture for receiving the ignition cable (2), the retaining part (4) protruding from the cast resin portion (14); a shrink hose (3) acting as a sealing means surrounding the end portion of the ignition cable (2) concentrically, extending through the aperture of the retaining part (4) and beyond the retaining part (4); and a shrink sleeve (6) acting as additional sealing means concentric with the end portion of the ignition cable (2) and connected with the end portion of the ignition cable at least in one end region and with the retaining part (4) at least in another end region thereof so as to seal against moisture.

BACKGROUND OF THE INVENTION

The present invention relates to ignition coils, and, more particularly,to ignition coils having a high-voltage connection device or means forconnecting an ignition cable to a secondary winding of the ignitioncoil.

An ignition coil is known, comprising a primary winding embedded in acast resin portion, a secondary winding embedded in the cast resinportion and a high-voltage electrical connection device. Thehigh-voltage electrical connection device includes at least one contactpart electrically connecting a high-voltage end of the secondary coil toa conducting end portion of an ignition cable and a retaining partprotruding beyond the cast resin portion and provided with athroughgoing aperture. A high-voltage connection of an ignition cable toan ignition coil is known from the DE-OS 35 06 929, in which theignition cable end is introduced into an aperture of a connection towerand contacted by a pointed contact pin, with the contact pin beingelectrically connected via a contact wire to the end of a high-voltagewinding. The connection tower, into which the ignition cable isinserted, is sealed against moisture by a shroud.

It is further common practice to use plug-type contacts for theconnection of the high-voltage cable to the high-voltage winding. Theseplug-type contacts may be insulating plastic molded pieces. Such plasticmolded pieces do not always guarantee a low-loss transmission,particularly with extremely high voltages, where moisture haspenetrated, for example. In order to ensure safe handling of the highvoltage, the plastic molded pieces would need to be of larger dimension.However, that would have the disadvantage that the connection area wouldhave significantly larger dimensions and that the weight of the ignitionunit would also increase.

The aim is to develop a high-voltage connection which removes thisdisadvantage and ensures, with the minimum weight possible, a low-losstransmission of the high voltage from the ignition coil to the ignitioncable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an ignition coilhaving an improved high-voltage connection device for connecting thesecondary winding to at least one ignition cable.

According to the invention, the ignition coil comprises a cast resinportion; a primary winding embedded in the cast resin portion; asecondary winding embedded in the cast resin portion; at least onecontact part electrically connecting the high-voltage end of thesecondary coil to a conducting end portion of an ignition cable; aretaining part having a throughgoing aperture for receiving the ignitioncable, the retaining part protruding from the cast resin portion; ashrink hose acting as a sealing means surrounding the end portion of theignition cable concentrically, extending through the aperture of theretaining part and beyond the retaining part; and a shrink sleeve actingas additional sealing means concentric with the end portion of theignition cable and connected with the end portion of the ignition cableat least in one end region thereof and with the retaining part at leastin another end region thereof so as to seal against moisture.

In contrast, the ignition system in accordance with the invention hasthe advantage that the high-voltage connection has small dimensions andhence a low weight and that the electrical point well protected againstmoisture by multiple overlapping of various components.

Various embodiments of the above-described ignition coil according tothe invention are possible. Of particular advantages is the preferredembodiment in which a cast resin/air/cable transition region is replacedby a cast resin/retaining part/cable transition region. Since theflexible ignition cable does not therefore directly emerge from thecasting compound, the mechanical load is low at this point.

BRIEF DESCRIPTION OF THE DRAWING

The objects, features and advantages of the present invention will nowbe illustrated in more detail by the following detailed description,reference being made to the accompanying drawing in which:

FIG. 1 is a partially side elevational, partially cross-sectional viewof an ignition coil secondary winding with an improved high-voltageconnection means for an ignition cable according to the invention; and

FIG. 2 is a cross-sectional view of the ignition coil of FIG. 1 in ahousing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 show details of the ignition coil of an ignition systemwith a secondary winding 7 arranged in a housing 9, and primary winding10. A contact part 1 at the two high-voltage winding ends of thesecondary winding 7 is conductively connected to an ignition cable 2,with a shrink hose 3 being pulled over the ignition cable end, for thebetter bonding of ignition cable and cast resin. The ignition cable 2with the shrink hose 3 is held in a retaining part 4, with thetransition point T being sealed by an adhesive 5 and the ignition cable2, which protrudes from the ignition coil, being covered by anadditional shrink sleeve part 6 at the transition point T. FIG. 2, inaddition to a primary connection 11, again shows the connection point ofcontact part 1 and the ignition cable 2, and the level 8 of a cast resinportion 14 is indicated, up to which the housing 9 of the ignition coilis filled with curable cast resin.

The high-voltage connection means 3,4,6 shown in FIG. 1 is moreexplained in more detail in the following. Each of the contact parts 1of the secondary winding 7 is conductively and mechanically firmlyconnected to one of the ignition cables 2. The ignition cable end islocated within the ignition coil in the cast resin portion 14 which iscast into the ignition coil. Owing to the peculiarities of the material,the resin and the ignition cable bond only very poorly to each other. Inorder to avoid leakage current, the shrink hose 3 is pulled over theignition cable end. This shrink hose 3 has the characteristic that itbonds better with the resin to the outside, and, due to its sticky-likesurface, it forms a moisture sealing connection to the inside with theignition cable. Without any additional provision, the ignition cablewould be severely mechanically stressed at the transition point T of theresin/air/cable. This would occur, since the ignition cable is immovablyembedded in the resin but is movable at the point of emergence from theresin, i.e. there is the risk that the ignition cable can separate fromthe resin. To avoid this, the ends of the ignition cable with the shrinkhose 3 are pushed through corresponding apertures of the plasticretaining part 4, before they are connected at the contact parts 1 tothe secondary winding 10. The unit in accordance with FIG. 1 thusobtained is then inserted into the housing 9 shown in FIG. 2, with theretaining part 4 protruding slightly from the cast resin and thetransition point of cast resin/air/cable transformed into the transitionpoint of cast resin/retaining part/cable. This retaining part 4 thustakes on the mechanical function of the previously commonly employedplug-type contact, but it has the advantage that its dimensions are muchsmaller. In order to protect this transition point T from moisture orcontamination, for example, it is sealed by an adhesive 5 in such a waythat the adhesive extends, starting from the ignition cable, via theshrink hose 3 and into the retaining part 4--into the gap between theinner wall of the aperture in the retaining part 4 and the outer wall ofthe shrink hose 3 pulled onto the ignition cable 2--up to the resinlevel. To provide additional sealing, one of the ends of the shrinksleeve part 6 is then pushed over the end of the retaining part 4 whichprotrudes from the resin while, its other end rests against the ignitioncable 2 and is fixed to these parts so as to seal against moisture bythe adhesive 5. The various connection parts, such as shrink hose,retaining part, and shrink hose, overlap at their transition points.

In this way, a high-voltage resistant transition between thehigh-voltage winding and the ignition cable is formed which is furthercharacterized by its small size and light weight.

While the invention has been illustrated and embodied in an ignitioncoil with a high-voltage connection device for connecting a secondarywinding to at least one ignition cable, it is not intended to be limitedto the details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed is new and desired to be protected by Letters Patent isset forth in the appended claims.

We claim:
 1. Ignition coil comprising a cast resin portion; a primarywinding embedded in said cast resin portion; a secondary windingembedded in said cast resin portion; at least one contact partelectrically connected to an end portion of an ignition cable and to ahigh-voltage end of the secondary winding; a retaining part (4) having athroughgoing aperture for receiving said ignition cable (2), saidretaining part (4) protruding from said cast resin portion (14); ashrink hose (3) acting as a sealing means surrounding said end portionof said ignition cable (2) concentrically, extending through saidaperture of said retaining part (4) and beyond said retaining part (4);and a shrink sleeve (6) acting as additional sealing means concentricwith said end portion of said ignition cable (2) and connected at leastin one end region with said end portion of said ignition cable and withsaid retaining part (4) at least in another end region so as to sealagainst moisture.
 2. Ignition coil as defined in claim 1, furthercomprising an adhesive portion (5) acting as a further sealing means,said adhesive portion extending through an annular gap between saidshrink hose (3) and said shrink sleeve (6) up to said cast resin portion(14).
 3. Ignition coil as defined in claim 2, wherein said other endregion of said shrink sleeve (6) is pulled over said retaining part (4)and said end regions of said shrink sleeve (6) are fixed to saidretaining part (4) and said ignition cable (2) by said adhesive means(5).
 4. Ignition coil as defined in claim 3, wherein a central portionof said shrink sleeve (6) covers an end section of said shrink hose (3)protruding from said retaining part (4).